Where the 747F(reighter) Trounces the A380F is (despite the higher volume of the WhaleJet) is that it's 1 main cargo floor is very strongly supported for heavier loads in very dense capacity.
Whereas, the A380F, though possessing 2 cargo floors, is not designed for dense weights so it can only carry lighter yet bulky items such as FEDEX, DHL, UPS, etc. do.
My guess is that if Boeing builds a BWB freighter there will be both civilian and a military versions. I’m pretty sure Boeing will promote it as a replacement for the C-5A’s. I’m pretty sure the cargo floor on the military version will be heavy duty enough to support M1A2 Abrams tanks.